The present invention relates to an ion generator for use in a combustion apparatus, such as internal combustion engines and the like, the generator adapted to ionize air introduced into a casing for supplying the ionized air to an air intake section of the combustion apparatus.
Heretofore, ion generators have been provided in the art for supplying ionized air to intake manifolds of internal combustion engines so as to enhance the combustion efficiency of the internal combustion engines as the combustion apparatus with the aim of improving the fuel economy and reducing the air pollution. Such an ion generator has been disclosed by, for example, Japanese Examined Utility Model Publication No.3(1991)-39192.
The ion generator disclosed in this publication comprises, as shown in FIG. 12, a casing 91 including an intake port 92 formed in one end surface thereof, an exhaust port 93 formed in the opposite end surface thereof, an air-flow passage extending between the air intake port 92 and the exhaust port 93, and an ionization electrode 94 disposed in the air-flow passage. The ionization electrode 94 is comprised of a cylindrical outside electrode 94a surrounding the air-flow passage and an inside electrode 94b disposed inside of the outside electrode 94a and composed of a plurality of star-shaped electrodes. The air flowing through the air-flow passage is ionized by plasma discharge between the outside electrode 94a and the inside electrode 94b. The air thus ionized is supplied to an intake manifold of the internal combustion engine via the exhaust port 93.
The casing 91 further contains therein a high-voltage generator 95 for supplying a high voltage to the ionization electrode 94. The high-voltage generator 95 is formed by first placing its components in the casing 91 and then molding the components with an insulating resin material. The high-voltage generator 95 has its positive pole connected to the outside electrode 94a of the ionization electrode 94 and its negative pole connected to the inside electrode 94b, respectively.
The ionization electrode 94 is accommodated in a vessel 96 formed of an insulating resin material, thus insulated from the casing 91, which is comprised of an aluminum die-cast product.
Unfortunately, however, the ion generator of the above construction has suffered a short service life of the high-voltage generator 95 for supplying the high voltage to the ionization electrode 94 to effect plasma discharge. Intensive studies have clarified the cause of such a reduced service life of the high-voltage generator. That is, the outside electrode 94a of the ionization electrode 94 is set to the positive pole while the casing 91 is mounted to the vehicle body as grounded. Therefore, additionally to the plasma discharge between the outside electrode 94a and the inside electrode 94b, there occurs another plasma discharge between the outside electrode 94a and the casing 91, so that heat resulted from the former plasma discharge combines with heat resulted from the latter to overheat the high-voltage generator 95.